The data are from the Prospective Study of the Collaborative Study on the Genetics of Alcoholism (COGA). The COGA study, which began in 1989 to identify the vulnerability and protective genes for alcoholism, has been described elsewhere (Begleiter et al 1995 ; Reich et al 1998 (link); Nurnberger et al 2004 (link)); only a brief overview is provided here. High risk families were ascertained through probands in inpatient or outpatient treatment for alcoholism at 7 sites across the United States, with all first degree relatives who were aged 7 or older interviewed with a comprehensive, highly reliable and valid assessment (Bucholz et al. 1994 (link); Hesselbrock et al. 1999 (link)). In families with at least 2 affected first degree relatives of the proband, recruitment was extended to additional relatives with an expanded protocol that included neuropsychological and neurophysiological evaluations and collection of blood for DNA. Comparison families, drawn from various sources (e.g., dental clinics, drivers’ registries), were studied with the same protocol.
Beginning in late 2004, adolescent and young adult offspring in the COGA families who were born from 1982 onward (aged 12-22 at inception) and with at least one parent who had been interviewed in the original COGA study, were recruited into the Prospective Study. Every 2 years, participants are administered a comprehensive structured psychiatric diagnostic interview covering histories of alcohol, tobacco and illicit drug use, problems and disorders, as well as other psychiatric disorders, to obtain DSM-IV and DSM-5 (for substances) diagnoses. Questionnaires that focus on personality, impulsivity, drinking motives, response to ethanol, among others, are included. Subjects undergo neuropsychological and neurophysiological protocols that focus on resting state and cognitive function, including aspects of frontal lobe functioning. About 75% of the sample has been genotyped. Supplemental Table 1 contains the specific assessments included. All subjects provided written informed consent, and the study was approved by institutional review boards at each COGA site.
In targeting the age range that covers the period of highest risk for initiation and progression of drinking and associated problems, the Prospective Study has several advantages. Its inclusion of a wide range of birth cohorts, as opposed to a few or even a single cohort as in other designs (e.g. Golding et al., 2001 ; Poulton et al., 2015 ), permits the study of multiple developmental periods in a short time period. It is a high-risk sample, with many youth having at least one parent with AUD, and the parents and other adult generations are well characterized for substance use and other psychiatric disorders. The subjects are diverse, with over 25% of non-European American heritage. Lastly, longitudinal assessments cover not only self-reported behaviors but also neurophysiological, neuropsychological and genetic measures (although not used in this report). These attributes distinguish the Prospective Study from others and underscore its ability to characterize AUD development over time from a multi-faceted perspective.
The data analyzed here were collected from January 2005—June 2016; 3573 offspring from 2147 nuclear families in 901 extended pedigrees are included. Characteristics across 5 assessment waves are displayed in Table 1. For these analyses, information across all interviews was used, selecting data from the interview at which the behavior, problem, or disorder was first reported.